EP3380222B1 - Modular catalyst monoliths - Google Patents

Description

The present invention relates to a reactor R, preferably a high-temperature reactor with device D, the use of reactor R with device D and a process for the production of nitrogen oxides or nitric acid, each using reactor R with device D, each as defined in the claims .

Devices accommodated in reactors, for example in a basket-like shape, which as a rule, also for reasons of construction or strength, consist of materials with good thermal conductivity such as metal or metal alloys, for example steel, expand when the reactor is heated to operating temperature, for example, or heated up by the heat of reaction and contract when the reactor cools down.

If devices of this type contain easily displaceable, particulate, for example poured, fillings of cylindrical or star-shaped catalytically active or non-catalytically active particles, the thermal expansion differences between the device and said filling usually result in depressions - often irregular and funnel-shaped - in the edge area of the device Particles usually trickle or sag from the edge area of the device.

This is undesirable since the inhomogeneity of the filling usually results in deteriorated properties, for example with regard to its catalytic behavior. In the recesses in the edge area, for example, the flow rate of a gas is greater than in areas without an indentation, which usually reduces the residence time of the gas in the edge area, and there is also less catalytic surface area available for the reaction gas, which generally leads to lower catalytic conversions in the edge area and overall leads.

The devices described above may also contain, in addition to or instead of the particles mentioned, monolithic shaped bodies, for example of honeycomb shape, which frequently consist of pressed, extruded and/or sintered inorganic material which is usually brittle, fragile or susceptible to abrasion. As a result of the above-described expansion and contraction of the device described above, the monolithic shaped bodies can also start to move, for example rub against one another and break apart or fall over. This entails the same problems as described above for particle filling.

In addition, it is troublesome and inefficient to replace such monolithic catalytic molded bodies with fresh molded bodies one by one, and there is a risk of breaking such molded bodies when taking them out from or putting them into the receiving device.

It also happens relatively often that the reactors, often due to unsteady operation, break down unplanned and unintentionally and have to be repaired, for which you then have to remove the monolithic catalytic moldings mentioned in order to get to the repair site and after the reactor has been repaired Shape body must reinstall. The disadvantages described above are found, for example, in processes for preparing nitrogen oxides and/or nitric acid by oxidizing ammonia in the presence of a catalyst, for example a catalyst gauze containing noble metals. In this case, the oxidation products of the ammonia are usually passed through a bed of a particulate and/or a bed of a nitrous oxide decomposition catalyst consisting of monolithic shaped bodies, which is usually located in a basket-like device. In this process, for example, the above-mentioned funnel-shaped depressions or also destruction or disorder of the monolithic shaped bodies in this bed or bed of nitrous oxide decomposition catalyst lead to reduced decomposition of the nitrous oxide in the catalyst bed, which in turn usually results in higher nitrous oxide emissions from the production plant, which is undesirable are.

A structured packing (for example hexagonal or cubic) of shaped catalyst bodies (modular structured fixed-bed reactor, "MOSFIBER") for the decomposition of, for example, dinitrogen monoxide (N ₂ O) in a reactor is out WO 2006/009453 A1 (Yara International ) known. WO 2006/009453 A1 however, is silent on the problem of abrasion or breakage of these shaped catalyst bodies during operation of the reactor and their replacement with new shaped catalyst bodies.

WO 2015/022247 A1 discloses a reactor with a device containing a gas- and/or liquid-permeable base in the edge region of which a side boundary is arranged, which completely encloses the base and forms a volume V containing shaped bodies, with at least there is a mesh made of metal. WO 2015/022247 A1 deals with the problems caused by the differential thermal expansion of different materials.

The object of the present invention was to provide a reactor with a device, the latter containing catalytic monolithic shaped bodies which are practically not damaged or destroyed during operation of the reactor and which can be completely or partially integrated efficiently and practically without being damaged or destroyed. and/or expand.

Accordingly, the reactor R, preferably a high-temperature reactor, with the device D, the use of the reactor R with the device D and a process for the production of nitrogen oxides or nitric acid each using the reactor R with the device D, each as defined in the claims , found.

In a preferred embodiment of the invention, the reactor R with the device D, each as described below, is used in a process for the production of nitrogen oxides and/or nitric acid. This embodiment is also referred to as “NOx/HNO ₃ embodiment” below, and the following applies expressly—unless otherwise stated—in particular to the NOx/HNO ₃ embodiment.

Processes for the production of nitrogen oxides and/or nitric acid, usually by catalytic oxidation of ammonia with an oxygen-containing gas, usually air, are known and are described, for example, under Nitric Acid, Nitrous Acid, and Nitrogen Oxides" in Ullmann's Encyclopedia of Industrial Chemistry, Sixth, Completely Revised Edition, Volume 23, pages 1 to 49, 2003, Wiley-VCH Verlag GmbH & Co . KGaA, Weinheim.

In a process for the production of nitrogen oxides and/or nitric acid, a mixture of ammonia and an oxygen-containing gas, for example air or else pure oxygen, is usually catalytically reacted at a relatively high temperature, for example in the range from 800 to 900 °C, for example on a network of noble metal such as platinum or platinum-rhodium alloy, and the resulting reaction products, which usually contain nitrogen monoxide as the main component and nitrous oxide ("laughing gas") as a minor component, usually flow through a bed with catalytic and/or non-catalytic, usually ceramic , to the reaction conditions in the reactor-resistant shaped body, which is arranged in the flow direction downstream, usually below the catalyst gauze.

This bed is usually catalytically active in the decomposition of nitrous oxide, usually contained in a basket-like device, and typically breaks down the nitrous oxide into the elements nitrogen (N ₂ ) and oxygen (O ₂ ). After the reaction mixture has left the device, which is usually basket-like, it is usually cooled on heat exchangers, during which it reacts further with oxygen to form nitrogen dioxide. The reaction mixture is generally further cooled via various heat exchangers—it being possible for nitric acid to condense out in some cases—and finally the reaction mixture is reacted with water in an absorption device to form nitric acid. The dilute nitric acid that may have previously condensed out in the cooling/condensation is usually also fed into the absorption device.

The invention is described in more detail below.

The material for the device D is usually a high-temperature material made of metal, for example Inconel 600 (material no. 2.4816), Alloy 602 CA, Haynes Alloy or also materials made from austinitic steels with the material designations 1.4828 and 1.4835. and 1.4876. The thermal expansion coefficients of these materials are usually in the range of 17 × 10 ^-6 K ^-1 to 19 × 10 ^-6 K ^-1 at an operating temperature of 800 - 900 °C.

A well suited material for the device D is Inconel 600 or steel with material number 1.4835 or Alloy 602 CA or Haynes Alloy.

Preferred materials for the device D are Inconel 600, steel with the material number 1.4835 or Alloy 602 CA.

The bottom B of the device D is generally perforated, with the type and geometry of the perforation not being critical and in particular permeable to gases and/or liquids, preferably gases. The bottom B is usually perforated in such a way that the particles that it usually carries cannot fall through the perforation.

In one embodiment, the floor B contains a support part, for example a grate made of a frame or a metal honeycomb structure on which a metal floor net or several, for example two to three, metal floor nets, usually with different mesh sizes and/or different wire mesh thicknesses, can rest. The support part, for example a grate made of a frame or a honeycomb structure, can consist of one piece, but it can also be composed of several segments, preferably 2 to 8 segments, particularly preferably 4 to 6 segments, which can be easily fixed to one another, with the geometry of the segments can be varied, for example quarter circle segments, sixth circle segments, eighth circle segments, ergo "pie geometry".

The openings of the above ground nets can have any cross-sectional geometry, for example, rectangular, hexagonal, round.

The base B is usually made of the material 1.4835, Alloy 602 CA and Inconel 600, preferably Inconel 600 or Alloy 602 CA.

The cross-sectional geometry of the base B per se generally depends on the cross-sectional geometry of the reactor R in which it is usually accommodated. Preferably, the cross-sectional geometry of the tray B is the same as that of the reactor R in which the tray B is housed.

Angular, preferably square or hexagonal, particularly preferably rectangular or uniformly hexagonal cross sections come into consideration as the cross-sectional geometry for the base B and/or the reactor R in which it is accommodated.

Furthermore, practically round or elliptical cross-sections, preferably practically round or round cross-sections for the tray B and/or the reactor R in which it is accommodated, come into consideration as cross-sectional geometry for the tray B and/or the reactor R in which it is accommodated. Particularly preferably, the cross section of the base B and/or the cross section of the reactor in which it is accommodated is practically round or round.

The tray B can be mounted, for example, directly or via ceramic or metallic spacers on a cooler or heat exchanger arranged downstream under the tray B in the reactor R. The floor B can also be supported by a central inner support and lateral brackets that serve as supports.

The material for the side boundary W of the device D is usually the same as for the bottom B.

The side boundary W is arranged in the edge area of the base B in such a way that it completely encloses the base B and forms a space with the volume V that is partially or completely filled with catalytic and/or non-catalytic shaped bodies—as explained in more detail below is. In a particular embodiment, the side boundary can be firmly connected to the floor B, in which case a basket-like connection is formed.

The side boundary W is usually arranged relative to the bottom B at the angles of 45° to 135°, preferably substantially perpendicular. The side boundary W is usually straight, ergo practically not bent in the vertical direction.

The ratio of the height of the side boundary W to the inside diameter of the floor B is usually in the range from 0.04 to 0.2.

Usual heights of the side boundary W are in the range from 100 to 1000 mm, preferably 150 to 600 mm.

Customary clear diameters of the bottom B are in the range of 2500 to 6000 mm.

The side boundary W can, but does not have to, be made from one piece, but can also consist of individual parts or segments.

A heat-insulating layer S can advantageously be located at least on a part of the surface of the inside of the side boundary W, preferably in the area directly adjoining the bottom B upstream. The heat-insulating layer S can cover the area of the inside of the side boundary W, for example from 30% to practically 100%, preferably almost completely.

The heat-insulating layer S preferably covers at least the lower 30%, for example 30% to 90%, i.e. those parts of the surface of the inside of the side boundary W that are closest to the bottom B.

The heat-insulating layer S usually completely encloses the side boundary W on the inside thereof.

The heat-insulating layer S usually adjoins the inside of the side boundary W practically directly, that is to say practically without a gap, in the direction of the center point of the device D. The heat-insulating layer S can be on the side facing the center of the device D, for example on the contact side for the bed of particles or the shaped bodies, practically any cross-sectional geometry, for example from straight (rectangular) to oblique, for example in the form of a trapezium, curved inwards (concave) and outwards, i.e. the side facing the center of the device D - curved (convex), step-like with one or more steps .

The heat-insulating layer S can consist of one piece or can be composed of individual elements to give the desired cross-sectional geometry, as will be described in more detail below.

The thickness of this heat-insulating layer S, based on the diameter of the floor B, is usually in the range from 0.5% to 5%, for example 1.0%. For example, when the diameter of the bottom B is 2500 to 6000 mm, the heat insulating layer S is 50 mm thick.

The material for the heat-insulating layer S is selected from the group consisting of ceramic material, for example fireclay, microporous material and silicate fibers, with the aforementioned materials generally not decomposing in the temperature range from approx. 700 to 1100 °C and usually having a thermal conductivity in the range from 0.03 to 0.15 W/m/K.

Microporous materials are microporous siliceous substances containing highly dispersed silicic acid and opacifiers, which do not decompose in the temperature range from approx. 700 to 1100 °C and have a thermal conductivity in the range from 0.04 to 0.09 W in the temperature range from 700 to 1100 °C /mK have preferred, for example the products WDS ^® High and WDS ^® Ultra from Porextherm, see three-page data sheet version 1.4/15-02 10/HH WDS ^® High and three-page data sheet version 1.03/15-02 10/HH WDS ^® Ultra der Company Porextherm Dämmstoffe GmbH, Heisinger Strasse 8/10, 87437 Kempten, www.porextherm.com.

The heat-insulating layer S can be made up of plates with a thickness of, for example, 10 to 50 mm made of the aforementioned material, preferably the microporous siliceous substances, with the plates being adapted to the required shapes or cross-sectional geometries of the heat-insulating layer W.

In a preferred embodiment, the above-mentioned material, preferably microporous siliceous substances - preferably after they have been thermally pretreated at 850 °C - and/or silicate fibers in the form of mats, are housed in cassettes for the heat-insulating layer S (hereinafter also referred to as referred to as "insulating cassettes"), as described below, which can then generally be assembled to form the heat-insulating layer S, as described below.

An insulating cassette with encased insulating material is described below as an example.

The insulating cassette usually consists of a metal housing, for example made of high-temperature-resistant steel, which is filled with one or more insulating materials, such as the microporous material described above, preferably the microporous siliceous substances, and/or silicate fibers, the latter preferably in the form of mats. For example, the microporous material built into the insulating cassettes is spaced apart from the metal wall by silicate fiber mats and silicate fibers.

The metal housing of the insulating cassettes can consist of one or more metals, for example high-temperature materials such as Inconel 600, Alloy 602 CA usually on the insulating cassette side facing the higher temperature and material 1.4541 on the insulating cassette side usually facing the lower temperature.

These insulating cassettes are preferably parallelepipedal in shape, preferably with a slight curvature and creases or other overlapping means which may form a tongue and groove configuration and are illustrated, for example, in Figure 12, in which the reference numerals have the meaning given herein. The walls located on the faces of the cassettes, which usually form the fold and overlap areas of the joined cassettes, are usually made of thin metal gauge, for example to reduce the effective total heat transfer.

The wall thickness of the fold and overlapping area of the insulating cassettes is usually in the range of 0.2 to 0.5 mm and is usually less than the wall thickness of the remaining part of the thermal insulation cassette, which is usually in the range of 0.8 to 1.5 mm . Preferably, the fold and overlap areas of the insulating cassettes are embossed in a wavy pattern.

For example, to build up the heat-insulating layer S, the above-described insulating cassettes are arranged in segments on the inside of the side boundary W over the circumference, as shown for example in FIG. 13, in which the reference symbols have the meaning given herein.

The insulating cassettes are preferably equipped with a sliding fit or other superimposition techniques, for example tongue and groove, in the circumferential direction (tangential direction) and are free of movement, for example, only in the circumferential direction.

The insulating cassettes are usually joined together at the installation temperature, which is usually 0 to 30 °C, so that the joint width at the location where the insulating cassette is exposed to a higher temperature in the reactor R is larger than at the location where the temperature in the reactor R is lower , which usually means that the insulating cassettes fit together as closely as possible under increased operating temperature in the reactor R due to expansion with practically no stress or the formation of distortions.

In one embodiment, part of the side boundary W - with or preferably without a heat-insulating layer S - here called W1, be firmly connected to the floor B, completely enclose it and be relatively low, for example W1 has a height in the range of 50 to 150 mm. The second part of the side boundary W, here called W2, can be arranged as an "apron", for example in the form of a Z-shaped construction, on the reactor inner wall, completely enclosing it and preferably fixed, with the end of the apron W2 being inverted, for example, looking downwards U or V profile is formed. The side boundary W1 protrudes into the opening of this inverted Us or V. The fixed connection of the side boundary W1 to the floor B is brought about, for example, by welding. The heat-insulating layer S is, usually below any catalyst mesh that may be present, preferably in two parts and preferably designed in a sliding-fit configuration, with the upper of the two parts of the heat-insulating layer S usually being preferably firmly connected to the upper side boundary W2 and the lower part of the heat-insulating layer S not is firmly connected to the upper side boundary W2 in such a way that it can still move up and down in the vertical direction. A heat-insulating layer S can also be applied above any catalyst mesh that may be present, preferably covering the entire remainder of the side boundary W. In a variant of this embodiment, W1 cannot be firmly connected to the base B, but rather so reversibly connected that it can be detached from it and reconnected to it again in a few simple steps, for example by welding, plugging, screwing.

In a further embodiment, the side boundary W completely encloses the base B and is not firmly connected to it, but is arranged, for example, as an "apron" on the reactor inner wall, completely enclosing it and preferably fixed, with a circumferential wall between the lower end of the apron and the base B gap is.

Usually, at least in the area of the inner wall of the reactor R, where the device D is accommodated, between the inner wall of the reactor R and the outside of the side boundary W of the device D, cooling devices, for example with a heat-absorbing medium - for example water or molten salt - are arranged in pipes , for example in that the tubes are arranged in the form of a tube coil between the reactor inner wall and the outside of the side boundary W. Such cooling devices usually have the task of protecting the reactor wall from excessive heat by active cooling, at least in the region of device D and/or the reactor flanges.

In one embodiment, the cooling devices on the inner wall of the reactor R in the area of the device D can be replaced in whole or in part by a heat-insulating layer S as described herein.

In this case, the area of the inner wall of the reactor R, where the device D is accommodated, itself forms the side boundary W, on the inside of which the heat-insulating layer S runs at least partially, preferably completely and practically without gaps, as described above - preferably from the above described insulating cassettes - and for example up to a height in the range of 200 to 1200 mm, measured from the bottom B from upstream.

On the side opposite the tray B upstream there is at least one mesh made of precious metal, for example platinum, palladium, rhodium and/or noble metal alloys, for example containing the aforementioned noble metals, and/or at least one mesh made of non-precious metal, for example megapyr mesh (Kanthal network) - this usually for the mechanical stabilization of the precious metal network. The network of noble metal and/or non-noble metal described above is also referred to herein as "catalyst mesh".

The volume V of the device D contains catalytic and/or non-catalytic shaped bodies (F) as described below.

Non-catalytic shaped bodies (F) here are usually ceramic shaped bodies which are resistant to the reaction conditions in the reactor R and practically do not catalyze the reactions in the reactor R.

Catalytic shaped bodies (F) here are generally shaped bodies which catalyze one or more reactions taking place in the reactor R, for example the decomposition of dinitrogen monoxide (N ₂ O) to form nitrogen and oxygen.

The catalytic and/or non-catalytic shaped bodies (F) are selected from (i) shaped bodies (F1) in the form of right prisms whose base is selected from a triangle, rectangle, hexagon or fragments of these polygons or (ii) a combination of the Shaped bodies (F1) with the shaped bodies (F2) defined below, which are smaller than the shaped bodies (F1).

The base of the shaped body (F1) is that of a preferably regular triangle, a preferably regular rectangle, a preferably regular hexagon or fragments of these polygons. The parallel displacement of the polygon forming the base occurs perpendicularly to the base, resulting in a right prism as a geometric body. If the base of the right prism is rectangular, it is also called a cuboid. The boundary surface of the prism that is congruent and parallel to the base of the respective prism is called the cover surface, the entirety of all other boundary surfaces is called the lateral surface.

wobei V_k das Volumen des Formkörpers und A_k die gesamt äussere Oberfläche des Formkörpers ist. Beispielhaft sei der äquivalente Partikeldurchmesser für einen sogenannten "Strängling", ein zylindrischer Formkörper, als Formkörper F2 mit einem Durchmesser d = 3 mm und einer Länge l = 10 mm berechnet: Es ergibt sich ein A_k = 108,4 mm² und ein V_k = 70 mm³. Daraus errechnet sich Dp_äq = 6 × 70,7 / 108,4 = 3,91 mm.The “equivalent particle diameter” Dp _eq comes into consideration as a further parameter for describing the shaped bodies (F1) and in particular (F2). This is defined as follows: $${\mathrm{dp}}_{\mathrm{eq}}=6\times {\mathrm{V}}_{\mathrm{k}}{\mathrm{/A}}_{\mathrm{k}}.$$

where V _k is the volume of the shaped body and A _k is the total outer surface area of the shaped body. As an example, the equivalent particle diameter for a so-called "strand", a cylindrical shaped body, is calculated as shaped body F2 with a diameter d = 3 mm and a length l = 10 mm: A _k = 108.4 mm ² and a V result _k = ^70mm3 . From this, Dp _eq = 6 × 70.7 / 108.4 = 3.91 mm is calculated.

Preferably, Dp _eq of the shaped body (F1) is five to fifty times, preferably fifteen times to twenty-five times, as large as Dp _eq of the shaped body (F2).

The height of the shaped bodies (F1) in the form of a right prism can be equal to or less than the longest side length of the n-gon (n=3, 4 or 6) forming their base; the height of the shaped bodies (F1) is preferably in the form of a straight line Prisms larger than the longest side length of the n-gon forming their base (n = 3, 4 or 6) so that an elongated prism with a longitudinal axis results.

Fragments of the n-corners (n=3, 4 or 6) forming the base of the shaped body (F1) can be formed in any way, for example by cutting through the triangle along its height, through the rectangle along its diagonal or through the hexagon intersects two opposite corners to form a triangle or a trapezoid. This fragmentation in turn results in three-dimensional moldings (F1) in the shape of a right prism.

The shaped bodies (F1) in the shape of a right prism generally have a diameter or diagonal of the base area in the range from 20 to 100 mm, preferably from 50 to 75 mm, and a height in the range from 100 to 300 mm, preferably from 150 to 230 mm.

Catalytic shaped bodies (F1) as described above are usually so-called unsupported catalysts, ie those which do almost entirely without an inert support substance. Very suitable such shaped catalytic bodies (F2) are those that catalyze the decomposition of nitrous oxide (N ₂ O) and, for example, in DE 103 50 819 A , particularly in paragraphs [0015] to [0017]. They can be obtained, for example, by extrusion.

Catalytic shaped bodies (F1) as described above can also be those which have a body made of inert carrier material, for example cordierite, with one or more channels that run/run practically parallel to the longitudinal axis of the shaped body (F1) and its/their channel surface is each coated with a catalytically active material. The channels mentioned generally have square cross-sections and the number of channels per area is expressed in cpsi (cell per square inch) and is 400, for example For example, a channel width of 1.2 mm or 230 cpsi with a channel width of 1.6 mm (the wall thickness is deducted in each case). Such shaped catalytic bodies are also referred to as “monoliths”. Very suitable such shaped catalytic bodies (F1) are those which catalyze the decomposition of nitrous oxide (N2O) and which, for example, in EP 1 147 813 A2 or in WO 2006/009453 A1 are described.

The catalytic and/or non-catalytic shaped bodies (F2) are smaller than the shaped bodies (F1). Preferably, Dp _eq of the shaped body (F1) is 5 to 50 times, preferably 15 to 25 times, as large as Dp _eq of the shaped body (F2).

The catalytic and/or non-catalytic shaped bodies (F2) are usually regularly or irregularly shaped solid particles, generally with a length in the range from 3 to 30 mm and a diameter in the range from 2 to 10 mm, for example with a round or star-shaped cross section . Further catalytic and/or non-catalytic shaped bodies (F2) can be the following: high-flow rings, rings, spheres, strands, hollow strands or other solid particles and/or shaped bodies with dimensions similar to those described above.

Catalytic shaped bodies (F2) as described above are usually so-called unsupported catalysts, ie those which do almost entirely without an inert carrier substance. Very suitable such shaped catalytic bodies (F2) are those that catalyze the decomposition of nitrous oxide (N ₂ O) and, for example, in DE 103 50 819 A , particularly in paragraphs [0015] to [0017].

Groups of m to n shaped bodies (F1) are enclosed in a metal cassette which is open on the upstream side and closed off with a gas-permeable base on the downstream side, side to side and with their longitudinal axis (height) aligned in the vertical direction to form modules (M); m, n is an integer from 3 to 30 and n > m.

The base of the modules (M) is generally perforated--the type and geometry of the perforation not being critical--and in particular permeable to gases and/or liquids, preferably gases. The bottom of the modules (M) is usually perforated in such a way that the particles it carries cannot fall through the perforation.

The base area of the modules (M) is generally in the range from 0.25 to 1.5 m ² , preferably in the range from 0.5 to 1.0 m ² .

The geometry of the shaped bodies (F1) is advantageously selected such that they almost completely cover the cross section of the bottom of the module (M) when they are arranged side to side and with their longitudinal axis (height) aligned in the vertical direction with virtually no gaps. For this purpose, the above-described fragments of the shaped bodies (F1) are usually used in the inner edge region of the module (M) to fill any gaps. An example of the assembly of the modules (M) with shaped bodies (F1) and the practical area-wide coverage of the cross-section of the bottom B of the device D with the modules (M) is in figure 1 shown.

The space between the outermost moldings (F1) in the module (M) and the inside of the module (M) can be filled with a joint filling material, such as in figure 2 shown. Possible joint filling materials are: fabric, felt, mats or the like made of inorganic, preferably mineral material such as silicate that is resistant to high temperatures.

In the manner described, a layer of shaped bodies (F1) and, if appropriate, (F2) is produced which almost completely covers the bottom of a module (M). It is of course possible to build up a further layer of moldings (F1) and optionally (F2) or a plurality of further layers of moldings (F1) and optionally (F2) analogously to this first layer.

The walls of the module (M) are made of metal, preferably material 1.4835, Alloy 602 CA and Inconel 600, preferably Inconel 600 or Alloy 602 CA. Advantageously, the cassettes forming the modules (M), preferably on their walls, are fitted with devices, for example eyelets, which serve, for example, to easily remove the modules (M), individually or in combination, for example by pulling them out of the device D can remove.

The height of the walls of the cassettes forming the modules is at least as high as the length of the longest shaped body (F1) contained in them, preferably the height of the walls of the cassettes forming the modules is 5 to 30% higher than the longest height of the longest in moldings (F1) contained in them.

In a preferred embodiment, the height of the walls of the cassettes forming the modules (M) is so high that the upper edge of the walls abut the underside of the precious metal and/or non-precious metal mesh opposite the bottom B of the device D upstream. The volume in the module (M) created in this way and not filled by shaped bodies (F1) can be partially covered by a gas- or liquid-permeable layer of high-temperature-resistant inorganic, preferably mineral material such as aluminum oxide, for example foam ceramics, Berls saddles, or non-catalytic shaped bodies (F2). or preferably filled in completely. The complete filling has the advantage, for example, that the mesh made of precious metal and/or non-precious metal lying upstream from the bottom B of the device D is supported over the entire surface and thus practically does not sag. An example of this embodiment is in figure 2 shown.

The surface geometry of the bottom of a module (M) can be varied. It is advantageously chosen so that when the modules (M) are assembled side by side in a tessellation, they cover the cross-section of the bottom B of the device D almost completely. The surface geometry of the bottom of a module (M) can be the following: (a) polygonal, such as triangular, square or hexagonal, preferably quadrangular, for example rectangular, particularly preferably square, or hexagonal, particularly preferably uniformly hexagonal, or (b) polygonal, preferably irregular polygonal, particularly preferably irregularly square, one side of the polygon being formed by an arc of a circle. In figure 1 shown.

The modules (M), optionally with the participation of a joint filling material, are joined to one another, side surface to side surface, with a vertical alignment of the longitudinal axis of the shaped bodies (F1) in such a way that they practically completely cover the cross section of the base B.

The gaps or crevices that may form where the outer side surfaces of the cassettes forming the modules (M) abut or abut the inner surface of the side boundary W of the device D can preferably be filled with joint filling material. Suitable joint filling materials of this type are: fabric, felt, mats or the like made from high-temperature-resistant inorganic, preferably mineral material such as silicates, for example mats made from polycrystalline fibers.

1. a) Eine unterste Schicht katalytische und/oder nicht-katalytische Formkörper (F2), darauf eine Schicht oder mehrere Schichten von Modulen (M) mit katalytischen und/oder nicht-katalytischen Formkörpern (F1).
2. b) Eine unterste Schicht von Modulen (M) mit katalytischen und/oder nicht-katalytischen Formkörpern (F1) darauf eine Schicht oder mehrere Schichten von katalytischen und/oder nicht-katalytischen Formkörpern (F2).
3. c) Eine unterste Schicht entweder von Modulen (M) mit katalytischen und/oder nicht-katalytischen Formkörpern (F1) oder eine unterste Schicht von katalytischen und/oder nicht-katalytischen Formkörpern (F2) und darüber jeweils regelmäßig alternierend oder unregelmäßig aufeinandergeschichtet mindestens eine Schicht von Modulen (M) mit katalytischen und/oder nicht-katalytischen Formkörpern (F1) oder von katalytischen und/oder nicht-katalytischen Formkörpern (F2).

In addition, as described above, the volume V of the device D can be partially or completely filled with modules (M) and/or catalytic and/or non-catalytic shaped bodies (F1) and/or (F2), preferably in horizontal layers, in a variety of ways. preferably up to the lowest mesh of precious metal and/or non-precious metal, for example as described below under a) to c):

1. a) A bottom layer of catalytic and/or non-catalytic shaped bodies (F2), thereon a layer or more layers of modules (M) with catalytic and/or non-catalytic shaped bodies (F1).
2. b) A bottom layer of modules (M) with catalytic and/or non-catalytic shaped bodies (F1) thereon a layer or several layers of catalytic and/or non-catalytic shaped bodies (F2).
3. c) A bottom layer either of modules (M) with catalytic and/or non-catalytic shaped bodies (F1) or a bottom layer of catalytic and/or non-catalytic shaped bodies (F2) and at least one layer regularly alternating or irregularly stacked on top of that of modules (M) with catalytic and/or non-catalytic shaped bodies (F1) or of catalytic and/or non-catalytic shaped bodies (F2).

In the variants described, the layers are usually separated horizontally by devices such as horizontally arranged perforated metal sheets or metal nets, for example megapyr nets.

• ba) Eine unterste Schicht katalytische und/oder nicht-katalytische Formkörper (F2), darauf eine Schicht oder mehrere Schichten von katalytischen und/oder nicht-katalytischen Formkörpern (F1).
• bb) Eine unterste Schicht von katalytischen und/oder nicht-katalytischen Formkörpern (F1) darauf eine Schicht oder mehrere Schichten von katalytischen und/oder nicht-katalytischen Formkörpern (F2).
• bc) Eine unterste Schicht entweder von katalytischen und/oder nicht-katalytischen Formkörpern (F1) oder eine unterste Schicht von katalytischen und/oder nicht-katalytischen Formkörpern (F2) und darüber jeweils regelmäßig alternierend oder unregelmäßig aufeinandergeschichtet mindestens eine Schicht von katalytischen und/oder nicht-katalytischen Formkörpern (F1) oder von katalytischen und/oder nicht-katalytischen Formkörpern (F2).

In other highly suitable embodiments, the volume of the modules (M) itself can be partially or completely filled with catalytic and/or non-catalytic shaped bodies (F1) and/or (F2), preferably in horizontal layers, in a variety of ways, for example as below described under ba) to bc):

• ba) A bottom layer of catalytic and/or non-catalytic shaped bodies (F2), on top of which is a layer or more layers of catalytic and/or non-catalytic shaped bodies (F1).
• bb) A bottom layer of catalytic and/or non-catalytic shaped bodies (F1), on top of which is a layer or more layers of catalytic and/or non-catalytic shaped bodies (F2).
• bc) A bottom layer of either catalytic and/or non-catalytic shaped bodies (F1) or a bottom layer of catalytic and/or non-catalytic shaped bodies (F2) and above that at least one layer of catalytic and/or non-catalytic shaped bodies (F1) or catalytic and/or non-catalytic shaped bodies (F2).

The layers in the variants ba) to bc) described can be separated horizontally by devices such as horizontally arranged perforated metal sheets or metal nets, for example megapyr nets.

The reactor R can be a vessel for carrying out chemical reactions, preferably on an industrial scale.

Examples of such chemical reactions are oxidations of carbon-containing and/or nitrogen-containing compounds, preferably with oxygen-containing or halogen-containing gases. Examples of such oxidations are the usual combustion of petroleum, naphtha, natural gas, coal and the like, for example to produce heat and/or electrical energy; the catalytic oxidation of ammonia with an oxygen-containing gas, preferably air or pure oxygen, to form nitrogen oxides; the so-called ammoxidation of organic compounds with methyl groups or of methane with ammonia and oxygen to form nitriles or hydrogen cyanide.

Another example of such chemical reactions is the preferably catalytic conversion of nitrogen oxides, preferably nitrous oxide (N ₂ O), to form nitrogen and oxygen.

The reactor R is preferably a vessel for producing, preferably on an industrial scale, chemical products, for example for producing nitrogen oxides such as NO ₂ , N ₂ O, N ₂ O ₄ , NO and/or nitric acid and/or nitrous acid, inter alia, by catalytic oxidation of ammonia with an oxygen-containing gas, for example air; for the production of sulfur oxides such as SO ₂ , SO ₃ and/or sulfuric acid, sulfurous acid or other acids of sulfur oxides.

For example, the reactor R is a cylindrical vessel for producing, preferably on a large industrial scale, nitrogen oxides such as NO ₂ , N ₂ O, N ₂ O ₄ , NO and/or nitric acid and/or nitrous acid by catalytic oxidation of ammonia with an oxygen-containing Gas, for example air or pure oxygen. An embodiment that is well suited for this example is shown in FIG. 4, for example.

Another subject of the present application is the use of the reactor R with the device D, in a process for the production of nitrogen oxides by catalytic oxidation of ammonia, for example in the temperature range from 800 to 900 ° C and for example on a network of noble metal such as platinum or Platinum-rhodium alloy, with an oxygen-containing gas, for example air or pure oxygen and, if necessary, reaction of the nitrogen oxides with water to form nitric acid, it being expressly pointed out that all disclosures relating to the reactor R and/or the device D or other objects of the invention herein are contained in the aforementioned Subject matter of the present invention is expressly incorporated.

Another subject of the present application is a process for the production of nitrogen oxides, wherein ammonia is reacted in a reactor R with an oxygen-containing gas, preferably air or pure oxygen, for example in the temperature range from 800 to 900° C., catalytically, for example on a noble metal net , such as platinum or platinum-rhodium alloy oxidized and the resulting nitrogen oxides-containing reaction products, which usually contain nitrogen monoxide as the main component and nitrous oxide as a secondary component, flow through an arrangement of catalytic and/or non-catalytic shaped bodies (F) in a device D, which is usually arranged downstream in the direction of flow, usually below the catalyst gauze, allowing the arrangement of the catalytic and/or non-catalytic shaped bodies (F) and the device D to flow, in each case as previously described, and it being expressly pointed out w ird that all disclosure of the catalytic and / or non-catalytic shaped bodies (F), to the device D herein and / or the reactor R or other subjects of the invention herein is expressly incorporated into the above-mentioned subject matter of the present invention.

A further subject of the present application is a process for the production of nitric acid, wherein ammonia is reacted in a reactor R with an oxygen-containing gas, preferably air or pure oxygen, for example in the temperature range from 800 to 900 ° C, catalytically, for example on a net made of noble metal, such as platinum or platinum-rhodium alloy and the resulting nitrogen oxides-containing reaction products, which are usually nitrogen monoxide as the main component and nitrous oxide as a secondary component included, through an arrangement with catalytic and / or non-catalytic shaped bodies (F) in a device D, which is usually arranged downstream in the flow direction, usually below the catalyst mesh, flows, usually cools, reacting with oxygen to form nitrogen dioxide and reacted with water to form nitric acid, the arrangement of the catalytic and/or non-catalytic shaped bodies (F), the device D and the reactor R, each as previously described, it being expressly pointed out that all disclosure relating to the catalytic cal and / or non-catalytic shaped bodies (F), to the device D herein and / or the reactor R or other objects of the invention herein is expressly incorporated into the above-mentioned subject matter of the present invention.

Exemplary embodiments are also shown in the figures and are explained in more detail in the following description.

List of reference numbers for the figures

1

reactor wall

2

joint filler

3

wall of a module (M)

4

Shaped body (F1)

5

[EMPTY]

6

Module (M)

7

Bottom of a module (M)

8th

Mesh of precious metal and/or non-precious metal

9

compensating body

10

Bottom B of device D

11

Side boundary W of device D

12

U-shaped apron

13

Pipes for cooling medium

figure 1 Figure 12 shows in cross-section part of a cylindrical reactor R, preferred for the NO _x /HNO ₃ embodiment, in which device D is housed. Shown are: The reactor wall 1, 11, the side boundary W of the device D, the modules 6 housed by the walls 3, the joints between the modules (M) 6 themselves and between the modules (M) 6 and the reactor wall 1 being filled with joint filling material 2 are filled out. The modules (F1) 4 are in the modules M. The modules (M) 6 cover the cross-section of the bottom B almost completely.

figure 2 shows a longitudinal section through a module (M) 6, among other things. It shows: the wall 3 of a module (M) 6, the floor 7 of a module (M) 6, the floor B 10 on which the modules (M) rest, the shaped bodies (F1) 4, which are enclosed in the modules (M), the joint filling material 2, the mesh made of precious metal and/or non-precious metal 8. The space between the shaped body (F1) and mesh 8 is equipped with a gas and/or or liquid-permeable layer of high-temperature-resistant inorganic material, the compensating body 9, filled.

figure 3 is analogous to figure 2 including the corresponding reference numbers and shows in longitudinal section a part of a cylindrical reactor R - preferably for the NO _x /HNO ₃ embodiment - in which the device D with modules (M) 6 is accommodated. A U-shaped metal apron 12 is fastened on one side to the reactor wall 1 by means of a flange. On the other side of the metal U-shaped skirt 12, the side boundary W 11 of the device D is attached. The U-shaped apron 12 encloses part of the tubes for a cooling medium 13.

examples General

An ammonia-air mixture (12.5 vol% NH ₃ , 87.5 vol% air) is fed to the cylindrical ammonia combustion furnace (reactor R) in which a device D in the form of a basket with a round bottom cross-section is accommodated. The basket-like device D has an internal diameter of 3.52 m. The reactor R is operated with an ammonia/air mixture throughput of 3650 Nm ³ /h and per m ² of catalyst mesh surface. The inlet temperature of the ammonia-air mixture in reactor R is 28.4° C. and the pressure upstream of the platinum catalyst gauze in reactor R is 1080 mbar (abs.). The ammonia burns on the platinum catalyst gauze at temperatures of approx. 880° C. to form the reaction product, which is then passed through device D, containing a catalytically active filling and containing nitrogen monoxide as the main component and small amounts of nitrous oxide N ₂ O ("laughing gas"). The nitrous oxide concentration of the reaction product is about 1000 ppm directly after the platinum catalyst gauze, ie before it hits the catalytically active filling of the basket-like device D. Downstream of the platinum gauze is the basket-like device D, containing shaped catalytic bodies (F1) (according to the invention) or shaped catalytic bodies (F2) (not according to the invention), as described in more detail below.

The non-mesh parts of the basket-like device D are made of Inconel 600, the side border W is about 250 mm high.

Immediately after the platinum catalyst net (tapping point 1) and in the middle of the reactor R downstream just below the tray B of the device D (tapping point 2) and at the periphery of the reactor downstream just below the outer edge area of the tray B of device D (sample point 3), samples of the reaction product can be taken and analyzed for nitrous oxide concentration using the GC/MS method.

After nine months of operation of the reactor R, the device D and its filling is checked. Nitrous oxide concentrations are measured during reactor R operation.

Comparative example 1 (not according to the invention)

The basket-like device D with a round bottom cross-section initially contains a 150 mm high layer of catalytic shaped bodies (F2), namely all-catalyst extrudates, which covers the entire area, these extrudates having a star-shaped cross-section, a diameter of approx. 6 mm and a length of 5 to 30 mm and consist of a mixture of CuO, ZnO and Al ₂ O ₃ .

In the continuous process, an ammonia-air mixture is converted as described above.

The edge area of device D has a funnel-shaped depression in the form of a ditch with a depth of 96 mm in the catalytically active filling, the height of which in the edge area of device D is only 54 mm (150 mm before the start of the test).

The measured nitrous oxide concentration at extraction point 3 practically below the funnel-shaped recess is 676 ppm nitrous oxide, at extraction point 2 the measured nitrous oxide concentration is 186 ppm so that the average measured nitrous oxide concentration downstream after device D and the downstream heat exchanger below is 227 ppm.

Example 1 (according to the invention)

The basket-like device D with a round bottom cross-section contains metal cassettes almost everywhere, as described below and in an analogous manner in figure 1 shown. 16 metal cassettes are used, which consist of square molds with external dimensions of 800×800 mm and molds adapted to the cylindrical side boundary of the device D or the reactor R. The cassettes are sealed with joint filling material among themselves and towards the cylindrical side boundary. The cassettes are filled with catalytic shaped bodies (F1) according to the invention in the form of a regular hexagonal prism or its fragments, as in figure 1 shown. These catalytic shaped bodies (F1) are so-called unsupported catalysts and essentially consist of a mixture of CuO, ZnO and Al ₂ O ₃ . They have a height of 160 mm.

In the continuous process, an ammonia-air mixture is converted as described above.

The measured nitrous oxide concentration at the extraction point 3 in the outer area of the device D, where in the case not according to the invention there was a funnel-shaped depression, is 84 ppm nitrous oxide, at the extraction point 2 the measured nitrous oxide concentration is 81 ppm, so that the average measured nitrous oxide concentration downstream after the device D and the downstream heat exchanger below is 82 ppm.

Claims (7)

1. A reactor R with apparatus D, the latter comprising a gas- and/or liquid-permeable tray B, in the edge region of which there is disposed a lateral boundary W which fully encloses the tray B and forms a volume V comprising catalytic and/or noncatalytic shaped bodies (F), wherein there is at least one braid made of precious metal and/or base metal on the upstream side opposite the tray B, and the catalytic and/or noncatalytic shaped bodies (F) are selected from (i) shaped bodies (F1) in the form of straight prisms, the footprint of which is selected from triangle, rectangle, hexagon or fragments of these polygons, and (ii) a combination of the shaped bodies (F1) with shaped bodies (F2) that are smaller than the shaped bodies (F1), wherein groups of m to n shaped bodies (F1), m and n being an integer from 3 to 30 with n > m, are framed in metal cassettes which form modules (M) and are open in the upstream direction and closed in the downstream direction by a gas-permeable tray, in a virtually seamless manner with side face to side face and with their longitudinal axis aligned in vertical direction, virtually completely covering the cross section of the tray, to form modules (M), and the modules (M), optionally with cooperation of a joint filler material, with vertical alignment of the longitudinal axis of the shaped bodies (F1), are joined to one another virtually seamlessly in a mosaic-like manner such that they virtually completely cover the cross section of the tray B.
2. The reactor R with apparatus D according to claim 1, wherein there is a thermally insulating layer S at least over part of the area of the inside of the lateral boundary W of the apparatus D, and the material for the thermally insulating layer S is selected from the group consisting of ceramic material, microporous material and silicate fibers.
3. The reactor R with apparatus D according to claim 1 to 2, wherein the cross section of the reactor R and of the tray B is virtually round in each case.
4. The reactor R with apparatus D according to claim 1 to 3, wherein the volume V of the apparatus D has been filled with catalytic and/or noncatalytic shaped bodies (F) up to a maximum of the lowermost braid made of precious metal and/or base metal.
5. The use of the reactor R as defined in claims 1 to 4 in a process for preparing nitrogen oxides by catalytic oxidation of ammonia with an oxygenous gas and optionally reaction of the nitrogen oxides with water to give nitric acid.
6. A process for preparing nitrogen oxides, wherein, in a reactor R as defined in claims 1 to 4, ammonia is catalytically oxidized with an oxygenous gas and the reaction products which comprise nitrogen oxides and are thus formed are allowed to flow through an arrangement of catalytic and/or noncatalytic shaped bodies (F) in an apparatus D, wherein the arrangement of the catalytic and/or noncatalytic shaped bodies (F) and the apparatus D are as defined in claims 1 to 4.
7. A process for preparing nitric acid, wherein, in a reactor R, ammonia is catalytically oxidized with an oxygenous gas and the reaction products which comprise nitrogen oxides and are thus formed are allowed to flow through an arrangement of catalytic and/or noncatalytic shaped bodies (F) in an apparatus D and then reacted with water to give nitric acid, wherein the arrangement of the catalytic and/or noncatalytic shaped bodies (F) and the apparatus D are as defined in claims 1 to 4.

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